Minister for Justice Jim O’Callaghan has condemned the Israeli government over drone attacks on a Gaza-bound flotilla carrying aid, and Irish as well as international pro-Palestinian activists.

It was a “reflection of the contempt that Israel has for non-combatants, whether they are in Gaza or international waters”, he said.

But he told TDs in the Dáil on Wednesday Ireland is not a “strong military power” and he could not “direct ‘marines’ or the Army Rangers” to rescue people, as Sinn Féin demanded action to protect Irish citizens on the flotilla.

The boats were attacked overnight by 12 drones, which prompted Italy to send a naval ship to come to the vessels’ assistance.

The Global Sumud Flotilla is attempting to break Israel’s naval blockade of Gaza. Those aboard include climate campaigner Greta Thunberg.

The organisers said in a statement at least 13 explosions were heard on and around boats and objects were dropped on at least 10 boats from drones or aircraft.

Tánaiste Simon Harris said in a statement the incident involving the flotilla were unacceptable.

“It is clearly a breach of international law to have any activity that is targeting civilians or a humanitarian flotilla,” he said in a statement from New York, where he is attending the United Nations General Assembly.

“This morning in New York, I have spoken directly with the EU’s High Representative and vice-president Kaja Kallas and to EU counterparts about collectively raising our concerns in Tel Aviv and considering what can be done to ensure the safety and wellbeing of all those on board the flotilla.

“I also intend to raise the matter publicly in my intervention at the United Nations during the Global Alliance for Implementation of the Two-State Solution meeting.”

Sinn Féin Senator Chris Andrews is among 22 Irish participants on the 51-vessel flotilla, most of which were in international waters off Greece when the attack happened.

In a statement Mr Andrews said the boat he was on, the Spectre, had been struck four times but there were no injuries or serious damage.

He said the Irish Government had a responsibility to protect its citizens on the flotilla and “as a matter of urgency they need to arrange for an observer vessel to accompany the flotilla to ensure Israel does not violate the human rights of its participants”.

His party leader Mary Lou McDonald raised the issue in the Dáil and described the attack as a “very serious development. This flotilla is in imminent danger.”

Mr O’Callaghan, expressing concern for Mr Andrews, said the flotilla was “going out lawfully protesting about the slaughter in Gaza” when it was attacked by Israeli forces.

The Minster also referred to Independent TD Barry Heneghan, who is not in the flotilla, but on a vessel due to sail on Wednesday.

Mr O’Callaghan condemned “the actions of the Israeli government in unlawfully attacking a lawful flotilla that is seeking to engage in peaceful activity in international waters”.

Labour leader Ivana Bacik also condemned the attacks and urged the Minister to “work with EU colleagues to ensure the safety of all those on that flotilla”.

The Minister told the Dáil officials in the Department of Foreign Affairs were closely monitoring the issue and would provide every support to the two Oireachtas members and other Irish members of the flotilla.

Mr O’Callaghan said they had to be aware of “the limits of Irish influence and Irish powers”.

He said “we are not a strong military power. I can’t direct ‘marines’ or members of the Army Rangers to go over and rescue people on that flotilla.”

Addressing Sinn Féin deputies, he said: “You know as well as I do the only action we can take is through the power of our influence by condemning this behaviour, and by trying to bring to the attention of the international community the totally unacceptable behaviour of the Israeli government. We’ve been quite effective at that, but that’s all we can do.”